The file-storage service competes with startups like Dropbox and giants like Microsoft and Google

Box, the eight-year-old company that has taken on industry giants to become a leader in cloud storage and file sharing, will seek to raise US$250 million by selling shares publicly for the first time.

The Los Altos, California, company announced on Monday that it had filed a registration statement with the U.S. Securities and Exchange Commission for a proposed IPO (initial public offering) of its common stock.

The company revealed in the filing that it has 25 million registered users, but it also says it has been losing money and might not post a profit for the foreseeable future.

Box has capitalized on the growing popularity among businesses of storing data in the cloud, where it can be accessed from a variety of devices including smartphones and tablets, giving employees more flexibility.

"Probably the biggest move in Box's trajectory was the decision to focus exclusively on business users," said Rob Koplowitz, an analyst at Forrester Research.

"That decision clarified their purpose and allowed them to be very direct and purposeful in hiring and technology investments. The strategy and platform they've been investing in will make or break them as an enterprise vendor," he said.

In the filing, which runs for about 150 pages, the company disclosed that it has more than 34,000 paying corporate customers and 25 million registered users.

The paying customers include more than 40 percent of the Fortune 500 and 20 percent of Global 2000 companies, according to Box.

The vast majority of its users don't pay, however. As of Jan. 31, 93 percent of its 25 million registered users were using the service for free. The other 7 percent were covered by corporate accounts or had paid for their own personal accounts, the filing reads.

Box also reveals that it isn't making any money. For its fiscal year ended Jan. 31, the company had revenue of $124.2 million, up 111 percent year on year, but its net loss was $168.6 million, deeper than its prior-year loss of $112.6 million.

Nor does it expect to be profitable for "the foreseeable future," because to grow its business it will need to continue investing heavily in sales and marketing, datacenter infrastructure and professional services, it said.

The company has already raised more than $300 million in funding from private investors, and the IPO news doesn't come as a surprise. CEO Aaron Levie told IDG News Service last year that the company could launch its IPO in 2014 or in 2015.

In a letter included with the filing, Levie said that the "freemium" model has worked well for the company. It has allowed it to enter enterprises via the initiative of individual employees who are looking for a file-sharing tool that's easier to use than traditional products, he said.

"We designed a product focused on the end user and created a business model that encouraged individuals within corporations to sign up for free. Whenever legacy systems prevented a marketing manager, sales person, or finance executive from accessing and sharing important information, Box was just a few clicks away," he wrote.

"To our surprise and delight, early users and IT administrators at sizable enterprises helped us refine and evolve our product to meet their needs and, by extension, the needs of other large organizations," he added. "It's been a thrilling ride. But it's also just beginning."

The filing includes a list of risks and challenges the company faces, including its losses, its limited operating history, the intense competition, the dangers of mismanaging its fast growth and concerns about security and potential breaches.

The IPO will be the latest barometer of investor enthusiasm for technology stocks, and an indicator of how the future may look for this segment of the market.

"There are a lot of vendors and offerings in this space. Many will fall by the wayside as leaders emerge," Forrester's Koplowitz said via email. "Depending upon how well this IPO goes for Box, the landscape in general will feel the effect in terms of valuation and future investment opportunities."

For Box, the decision has its potential pluses and minuses. "An IPO signals maturity and stability to the market. That should be a positive for customers and prospects," Koplowitz said.

On the other hand, a publicly traded company has more pressure to deliver quarterly progress and respond to those shareholders, which can affect long-term strategies, he said.

With Box's rise to prominence, Levie has become an industry celebrity. At 29 he is seen as a wunderkind who had the vision to co-found a cloud company and guide it to become a market leader. He and co-founder Dylan Smith, the CFO, were still in college when they started Box.

Last year, Forrester evaluated enterprise storage and file-share products from 16 major vendors and ranked Box at the top. Forrester used criteria like mobile access, administration controls, security, sync capabilities and integration with third-party systems. It also factored in how well it positions the company for future improvements and growth.

Ranking just below Box were EMC's Syncplicity and IBM's Connections enterprise collaboration suite, which has a file sync and share component based on IBM's FileNet architecture. Coming in below were products from Citrix, Accellion, Egnyte and WatchDox, followed by offerings from AirWatch, Alfresco, Dropbox and Salesforce.com.

Other Box competitors include YouSendIt, as well as larger players like Microsoft, with its SkyDrive and SharePoint services; and Google, with Apps and Drive.

Box grew its staff from 369 employees in early 2012 to 972 employees as of Jan. 31, 2014.

Morgan Stanley, Credit Suisse and J.P. Morgan will be "book-running" managers for the offering. BMO Capital Markets will act as lead manager, and Canaccord Genuity, Pacific Crest Securities, Raymond James & Associates and Wells Fargo Securities will act as co-managers.